南亚热带特大型水库季节性分层特征研究

Study on Seasonal Characteristics of Thermal Stratification of a Large-scale Reservoir in South Subtropical China

新丰江水库是典型的南亚热带深水贫营养水库。为了解其水库的季节性分层特征,于2020年3月—2021年2月,对水库的水温,溶解氧(DO),pH值,总磷(TP),总氮(TN),高锰酸盐指数(I_(Mn))和叶绿素a浓度(Chl.a)季节动态和垂直分层结构进行分析。结果表明,水库分层时间较短,混合期为1—4月和11—12月,热分层期为5—10月,夏季和秋季出现明显分层现象。水体分层结构对DO,pH值,TN,I_(Mn)和Chl.a的垂直分布有一定影响作用。水库未出现较明显的DO分层和季节性缺氧现象,水库表层水体DO值大于《地表水环境质量标准》(GB 3838—2002)中I类水质标准值(7.5 mg/L),但是水体温跃层内DO值从Ⅰ类下降为Ⅱ—Ⅲ类,说明其可能面临潜在的生态风险,不利于水生态环境系统的稳定。

Xinfengjiang Reservoir is a typical large-scale oligotrophic subtropical reservoir in southern China.The investigation on the seasonal and vertical dynamics of water temperature,dissolved oxygen(DO),pH value,total phosphorus(TP),total nitrogen(TN),permanganate index(I_(Mn))and chlorophyll a(Chl.a)was conducted from March 2020 to February 2021 in order to find out the seasonal stratification characteristics of Xinfengjiang Reservoir.Results showed that the reservoir had a significant seasonal thermal stratification in summer and autumn,and the thermal stratification period was during May to the end of October,and the mixed period were during January to April and during November to December.Thermal stratification had influences on vertical distribution of DO,pH value,TN,I_(Mn) and Chl.a.Strong stratification of DO and seasonal hypoxia didn't appear,the DO value of surface water was higher than class Ⅰ level(7.5 mg/L)set by“Environmental quality standards for surface water”(GB 3838—2002),but the D0 value of thermocline layer descended from Class Ⅰ to Class Ⅱ-Ⅲ.It indicates that it may face potential ecological risks,which is not conducive to the stability of the aquatic ecological environment system.